Any idea where I can find a washer fluid reservoir cap that fits without having to buy the entire bottle?

 

Local you pull it?

 

the mazda3 has the same washer fluid cap. Your local pick-n-pull or equivalent parts yard will likely have more mazda3s than mazda5s. I grabbed a washer fluid cap from a 2012 3 for my 5 and it fit perfectly. Cost maybe $2

 

I grabbed one off of a 04 Mazda 6 and it’s worked great.

 

Glad you figured it out!